Hi Duncan, > Hi Bill, does a branch instruction have side-effects?
Yes. > What is a side-effect? I noticed some confusion in gcc about > the definition of a side-effect, so it would be good to avoid > confusion in LLVM. > My understanding of a side effect is when an instruction has un-modeled effects. For instance, "emms" on X86 has side effects that aren't modeled in the instruction pattern -- it resets the FP registers after MMX use. Other instructions have no un-modeled side effects -- e.g., "xor" on X86 or "li" on PPC. Others may have un-modeled side effects in some situations, but not in others -- e.g., loads, in general, have side effects (accessing memory), but loads from a constant pool don't. This is the working definition, anyway. In the beginning, it'll be closely tied to what the "isRematerializable" flag means. I don't know what GCC considers side effects. Could you give a summary? It would be good to contrast/compare with it. -bw _______________________________________________ llvm-commits mailing list llvm-commits@cs.uiuc.edu http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
